The present invention relates to construction of columns and cartridges for use in preparing samples for chemical analysis, such as for chromatographic analysis. In particular, the construction of the present invention relates to housings such as microcolumns and cartridges, that are useful for separating an analyte of interest from a sample solution. The invention is adaptable for providing a wide variety of microcolumn and cartridge embodiments that can be easily adapted for separation of a range of selected analytes from solution.
A wide range of devices for use in containing a sorbent material for use in solid phase extraction of samples in chemical analysis are known. Some of these devices are in the form of cartridges and some are in the form of miniature chromatography columns. These devices provide a housing for a sorbent material, with the sorbent material being retained within the housing during flow of a fluid such as a solvent through the sorbent material by a porous retaining element. The porous retaining element is usually described as being a frit. The frit may be a porous glass plate, a porous polymeric plate, or a supported porous membrane. These various types of frits may be held within the housing of the extraction device by a constriction or narrowing of the housing. The present invention discloses a new construction for extraction devices, that comprises a new way of supporting a porous retaining element for a sample extraction device.
An example of a typical sorbent retaining construction that has been used in the prior art may be seen in U.S. Pat. No. 5,368,729 to Stefkovich et al. This patent discloses a sample extraction device in the form of a column, and having a constriction at its lower end. The constriction forms a shoulder, upon which a frit is supported, the frit serving to retain a solid phase sorbent used for extraction of a sample.
Another example of a device that is known in the art for extraction of a sample is disclosed in U.S. Pat. No. 5,658,800 to Lessard et al. This patent discloses a cartridge in the form of a column, the cartridge containing layers of a sorbent material. The layers are retained within the cartridge during use for sample extraction by xe2x80x9cfrits or filters.xe2x80x9d Retention of the sorbent layers appears to be by having a constriction in the bottom of the cartridge, or by having the frit or xe2x80x9cfilter dimensioned to fit snugly within the inner diameter of the barrelxe2x80x9d of the cartridge. This indicates that the element for retaining a sorbent in the cartridge, as disclosed by Lessard, is held in place in the cartridge by a close fit of the element to the inner diameter of the barrel of the cartridge, or of the inner diameter of the barrel to the element.
A construction for retaining a sorbent material within an extraction device was disclosed in U.S. Pat. No. 5,454,951 to Hoopman, that provides a disk shaped element having concentric, radially-spaced apart grooves. The disk shaped element disclosed there uses the grooves and the a plurality of radially-extending grooves to control the flow of liquid from a sorbent layer through a tortuous path above the disk shaped element, to peripherally-located openings in the disk shaped element. In Hoopman there is no teaching of a support for this disk shaped element.
The retaining members known in the art for retaining a sorbent within a cartridge or column, have generally been simple constrictions near the bottom of the cartridge or column. The simple constrictions provide support for a rigid frit, that serves to retain a sorbent material within the cartridge or column, with the frit being porous to allow flow of a solvent through the sorbent and the device. It is known to users of such devices that when a solvent is passed through the device, sputtering of the solvent sometimes occurs below the frit, leading to the elution of a sample being less clean than the user wishes. That is, cross-contamination of samples being eluted from such devices is known to be a problem. Also, it is known in the art that the passage of a solvent through such devices is sometimes subject to channeling effects through the sorbent that make the desired separations below the optimum that might be achieved. There remains a need in the art for a housing for use in sorbent based analytical sample preparation that can be manufactured economically, is adaptable to varied embodiments, and that provides support for a sorbent retaining frit while reducing the sputtering that occurs with known devices. The housing of the present invention as described herein meets these needs.
To overcome the shortcomings of known extraction cartridges and columns, we have now designed a new housing for containing a solid phase extraction sorbent.
Briefly, a housing construction is disclosed here that can be used to retain a sorbent material within an extraction device. The new construction is for a housing that comprises a plurality of projections within the housing, these projections providing a supporting profile to support a retention member, the retention member supporting the sorbent material used in the housing for purposes of preparing a sample for a chemical analysis.
The new housing can be used for containing a sorbent used in chemical analysis sample preparation. This housing may be used in the form of a column, a cartridge, or an extraction module.
The extraction device of the present invention can be made from any material that is not appreciably soluble in the solvents used for chemical analysis. Examples of some materials that are acceptable with commonly used solvents include glass, polypropylene, polyethylene, polytetrafluoroethylene, and stainless steel. Preferred materials for use with the invention include polyolefin resins, such as polypropylene and polyethylene. More preferably, the inventive extraction device is constructed of a polymeric resin, such as a polypropylene. An example of a polymeric resin that is especially preferred for use with the present invention is a polymeric resin such as Aristech(trademark) F120F, available from Aristech Chemical Corp., 210 Sixth Ave., Pittsburgh, Pa. 15222, U.S.A. The use of a resin such as the indicated resin allows the housing to have a reduced degree/level of plasticizers or other polymer additives in contact with a fluid/solvent used in chemical analysis.
It is accordingly an aspect of the invention to provide a housing for a sorbent used in analytical sample preparation where the housing incorporates the ability to support the sorbent with a sorbent retention member using spaced apart ridges projecting from the housing.
It is another aspect of the invention to provide a sample extraction device that can be manufactured easily from a polymer resin.
It is another aspect of the invention to provide a sample extraction device that is made with a construction that provides for support of a sorbent retention member, and that provides for channeled flow of a solvent fluid from the sorbent retention member out of the extraction device.
These aspects, and others set forth more fully below are achieved by the present invention.